[PATCH 6.1 068/473] mm/slub, kunit: Use inverted data to corrupt kmem cache

Greg Kroah-Hartman
2024-06-06T14:13:14Z

From: Guenter Roeck <linux@roeck-us.net>

[ Upstream commit b1080c667b3b2c8c38a7fa83ca5567124887abae ]

Two failure patterns are seen randomly when running slub_kunit tests with
CONFIG_SLAB_FREELIST_RANDOM and CONFIG_SLAB_FREELIST_HARDENED enabled.

Pattern 1:
# test_clobber_zone: pass:1 fail:0 skip:0 total:1
ok 1 test_clobber_zone
# test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:72
Expected 3 == slab_errors, but
slab_errors == 0 (0x0)
# test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:84
Expected 2 == slab_errors, but
slab_errors == 0 (0x0)
# test_next_pointer: pass:0 fail:1 skip:0 total:1
not ok 2 test_next_pointer

In this case, test_next_pointer() overwrites p[s->offset], but the data
at p[s->offset] is already 0x12.

Pattern 2:
ok 1 test_clobber_zone
# test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:72
Expected 3 == slab_errors, but
slab_errors == 2 (0x2)
# test_next_pointer: pass:0 fail:1 skip:0 total:1
not ok 2 test_next_pointer

In this case, p[s->offset] has a value other than 0x12, but one of the
expected failures is nevertheless missing.

Invert data instead of writing a fixed value to corrupt the cache data
structures to fix the problem.

Fixes: 1f9f78b1b376 ("mm/slub, kunit: add a KUnit test for SLUB debugging functionality")
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
CC: Daniel Latypov <dlatypov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/slub_kunit.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
index 7a0564d7cb7ae..9384747d90e5f 100644
--- a/lib/slub_kunit.c
+++ b/lib/slub_kunit.c
@@ -39,7 +39,7 @@ static void test_next_pointer(struct kunit *test)

ptr_addr = (unsigned long *)(p + s->offset);
tmp = *ptr_addr;
- p[s->offset] = 0x12;
+ p[s->offset] = ~p[s->offset];

/*
* Expecting three errors.
--
2.43.0